A conventional polarizing plastic lens is illustrated in FIGS. 2 and 3 of Japanese Laid-Open Patent Publication No. 2001-311804. Such polarizing plastic lens includes a polarizing film made of polyvinyl alcohol resin held within a lens made of diethylene glycol bis(allyl carbonate) resin.
The polarizing plastic lens is manufactured using an annular gasket and a pair of mold members. The gasket has an inner surface formed with a supporting protrusion and an outer surface including two resin injection pipes. The two mold members are fitted to the inner surface of the gasket.
When manufacturing the polarizing plastic lens, the peripheral edge of the polarizing film is first placed on the supporting protrusion of the gasket, and then the two mold members are fitted to the inner surface of the gasket. A cavity is thus defined between the two mold members, and the polarizing film is arranged in the cavity. Diethylene glycol bis(allyl carbonate) resin is injected into the cavity through the resin injection pipes. The resin is polymerized and cured. The molded polarizing plastic lens is obtained by removing the mold members from the gasket.    Patent Publication 1: Japanese Laid-Open Patent Publication No. 2001-311804
However, in the conventional polarizing plastic lens, the lens and the polarizing film each have a different coefficient of thermal expansion. Thus, the polarizing film tends to separate from the lens when an environmental change such as temperature change occurs.